Production printing systems for high-volume printing typically utilize a production printer that marks a continuous-form print medium (e.g., paper) with a wet colorant (e.g., an aqueous ink). After marking the continuous-form print medium, a dryer downstream from the production printer is used to dry the colorant applied to the continuous-form print medium. Microwave dryers may be employed as a dryer for a production printing system in some applications.
A microwave dryer utilizes microwave energy to heat the colorant to cause a liquid portion of the colorant to evaporate, thereby fixing the colorant to the continuous-form print medium. A microwave source directs the microwave energy down a long axis of a waveguide, and a passageway through the waveguide is sized to enable the continuous-form print medium to pass through the waveguide. As the continuous-form print medium traverses the passageway, the wet colorants applied to the continuous-form print medium are exposed to the microwave energy and are heated.
Due to the high speeds used in production printing systems, the amount of time that a particular portion of the continuous-form print medium is within the passageway can be short. To ensure that the colorant can be dried, the length of the waveguides may be extended and/or the number of waveguides may be increased and/or the power of the microwave energy used to dry the colorant may be increased. However, longer or more waveguides require more floor space in a production printing environment, and increasing the power of the microwave energy can add cost to the operation of the printing system.